The United States National Library of Medicine defines muscle tone as “the state of activity or tension of a muscle beyond that related to its physical properties, that is, its active resistance to stretch.” Muscle tone is what enables an individual to move or maintain a specific posture. Individuals whose muscles are in a hypertonic or hypotonic state such as, respectively, spastic cerebral palsy patients or astronauts, have extreme difficulty controlling various muscle groups and are in need of alternative therapeutic modalities. Current clinical practices address these issues either pharmacologically or surgically, but provide less than desirable results. Less invasive modalities delivering longer periods of altered muscle tone are needed most when addressing quality of life issues and rehabilitative success.
It is known that the human vestibular system provides a peripheral sensory function and resultant motor information for the brain. Specifically, two otoliths per ear sense linear accelerations; namely the Utricle, which senses horizontal, earth-horizontal linear accelerations and static head tilt, and the Saccule, which senses vertical acceleration. In addition, three semicircular canals sense angular accelerations. The motor output of the vestibular system (the Vestibulo-Spinal Reflex (VSR)) drives skeletal muscles such as anti-gravity muscles (extensors of the neck, trunk, and extremities), stabilizes head, and controls erect stance relative to gravity (push-pull mechanism).